The present invention relates in general to miniaturized object engagement devices, such as but not limited to actuators used for component seizure and manipulation in micro-tool systems and the like, and is particularly directed to a new and improved, diminished hardware-complexity and reduced power demand, current-controlled gripping mechanism. The gripping mechanism of the invention employs a pair of juxtaposed, mechanical spring-bias deflection element-supported (e.g., cantilever-mounted) electromagnets, to which respective object engagement elements (e.g., gripping pincers) are coupled. Current flow through the coils of the electromagnets provides mutual magnetic attraction that opposes the mechanical force of the spring-biased support members, so as to enable a pair of controllably manipulated gripping elements to seize an object. Reducing the controlled current flow through the electromagnets decreases the strength of their mutually coupled magnetic fields, so as to allow the spring force of the (cantilever) support members to controllably counter the gripping force imparted by the elements, and release the object.
As the relatively infant micro-tool industry has begun to expand and develop devices and components for a variety of utility applications, it has examined whether existing packaging and deployment technology may be utilized in considerably reduced scale systems, such as object engagement and displacement mechanisms employed in miniaturized gripping devices of the type employed in medical instruments, semiconductor processing pick-and-place robotic components, and the like. Currently existing technology for controlling these types of devices customarily falls into actuator categories that make them unattractive and impractical solutions to the present needs of micro-tool systems.
For example, a DC motor-controlled gripper requires a second motor as an auxiliary (fail-safe mode) unit (to ensure that the gripper will return to its open position). Moreover, it cannot be actuated in the event of a power loss, and has a relatively large number of parts, size and weight. Solenoid actuators are essentially on/off devices, so that they have no position control capability, dissipate substantial heat, and are relatively large in size and weight. Thermal switch actuators and piezoelectric devices are also position control-limited (too small a range of motion) and dissipate a substantial amount of heat. In addition, each of these types of actuator subsystems requires a multi-component mechanical interface, such as a gear train and associated linkage system, between the drive unit and the miniaturized element(s) being deflected or displaced.
In accordance with the present invention, these drawbacks of conventional positioning actuators are effectively obviated by an electrically (current) controlled object engagement (e.g., gripping) device, that is configured of a substantially reduced number of parts and operates with low power demand, that makes it especially suitable for micro-tool applications. The miniaturized gripping mechanism of the invention employs a pair of electromagnets that are supported in mutually juxtaposed positions by associated spaced apart deflection elements. In a preferred embodiment, the deflection elements comprise cantilevered arms to which both the electromagnets and object-engaging (gripper) elements are affixed.
In a non-limiting but preferred embodiment, the cores of the two electromagnets are configured as truncated bobbin-shaped elements, that are made of a low permeability ferromagnetic material (such as 430 F and 430 FR stainless steel), and provides a relatively low reluctance path for a magnetic field produced by current flow through the coils of the electromagnets, but rapidly loses its ferromagnetic properties once the energizing current is terminated. By controlling the flow of energizing current through the coils of the electromagnets, the magnitude of mutual (magnetic) attraction against the spring forces of their (cantilever-supported) deflection arms may be controllably defined. This allows the mutual separation between the object engagement elements to be controlled, so as to enable seizure, retention, and release of an object.
The geometry of the cantilever configuration results has a hysteresis current flow vs. displacement characteristic, that may be exploited to allow the coil energizing current to be reduced from an initial level that is required to close the gripping elements upon and seize an object, to a relatively low xe2x80x98sustainingxe2x80x99 current value that holds the same displacement between the gripping elements. Since the gripping elements can be held closed on the object at this reduced current, I2R-based heat loss in the coils is reduced. To release the object, it is only necessary to reduce (e.g., turn off) the energizing current, which reduces the magnetic fields in the two electromagnets and allows the spring force of the cantilever beams to return the gripping elements to their initial open positions.